Comformaker gas furnace ignites but blowe wont come on

My 10 old Comfortmaker gas furnace ignites and little fan works outside but main blower does not come on. I called my repairman...I have seen him deal with this a time or two over the years but I forgot. I know he removes the panel door but thats it!!! I am so afraid of gas. Can anyone tell me exactly whats NOT happening and how I can maybe make the fan come on?

I have a similar problem, when I switch from auto to fan the blower does come on. The furnace fires up but the fan does not come on in auto mode, then the furnace shuts down. Blower works fine in fan mode and eventually blows cold air once the furnace shuts off. Can anyone help diagnose this?

It may be a stuck fan limit control switch spring.

My Comfort Maker gas furnace had the very same symptoms, and I just fixed it. My problem was caused by a stuck fan limit control switch spring. This spring expands when the furnace heats up, rotating a dial which switches on the blower fan. To get to mine, I first switched off the power to the furnace. Then I took off the topmost removable panel (the one with horizontal vent holes in it) and sttoping down so that I could peer at the very top of the interior, I saw a metal box with "Honeywell" imprinted on it about 2" x 4" in size. This was the fan limit control switch. I removed it's cover and rotated the dial back and forth multiple times to loosen the stuck spring, then replaced the cover and turned back on the power to the furnace. I am now enjoying heat! This is very easy to do and only takes a few minutes. If this does not work, you may need to replace the fan limit control switch. The part number is written on the side of it, and may be ordered on eBay. To replace, just unscrew the retaining screws and unplug the wiring harness. Make sure the dial settings on the new switch are set the same as your old one first, though.

That fan/limit control actual has a warning stamped on the dial not to do what you did.
If turning it didn't put it out of calibration, then it just stopped that bimetal spiral strip spring from binding on something which is still there.
In my experience that is just a very temporary fix. The good news is it's not an expensive or hard part to change.

Thanks

I am not an HVAC profesional, so I very much appreciate your safety precautions, and urge all readers to follow your advice in this matter. My furnace is still working fine, but in light of your comments, I can see why the procedure I followed could potentially be dangerous, or may only be a temporary fix. Better to play it safe, and simply replace the fan limit control switch if you have a unit like mine.

Blower on Comfortmaker RPJ II

Hi,
I am having the same problem and would appreciate some advice.

The Blower of my 1993 Comfortmaker RPJ II will not come on when thermostat calls for heat. Blower comes on when thermostat is set to "ON". If i then turn thermostat to call for heat with blower in the "On" position the blower shuts off in a under a minute and then the burners go out too after a few seconds. The control board then flashes four times which indicates a 'Open high limit switch'.

Technician who came out to look at it think the board is fried and wants 600$ to replace it. He then hooked up the blower directly so that it is always running and thermostat calls for heat when it needs to.

Hoping for some suggestions to identify which part is causing the problem.

The Blower of my 1993 Comfortmaker RPJ II will not come on when thermostat calls for heat. Blower comes on when thermostat is set to "ON". If i then turn thermostat to call for heat with blower in the "On" position the blower shuts off in a under a minute and then the burners go out too after a few seconds. The control board then flashes four times which indicates a 'Open high limit switch'.

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You could try replacing the fan limit control switch. That was the culprit when my system had the very same symptoms.